Time series plot of weather conditions for Los Angeles International Airport [click to enlarge]

Some locations in southern California received record daily precipitation on 15 September 2015. A time series plot of weather conditions for Los Angeles International Airport is shown above; the 1.80 inches of rainfall received there made it the wettest September day on record.

As mentioned in the NWS Los Angeles record event report, the moisture source for this heavy rainfall event was the remnants of Hurricane Linda (storm path); the MIMIC Total Precipitable Water product covering the period 06-15 September (below) showed the evolution of the moisture associated with Linda, which originally tapped rich moisture from the Intertropical Convergence Zone (ITCZ).

MIMIC Total Precipitable Water product [click to play animation]

A closer look at the MIMIC Total Preciptable Water product (below) showed how the moisture was becoming more concentrated just offshore, in advance of an approaching upper level trough and a decaying surface cold front.